1. Field of the Invention
This invention is directed to a circuit for generating and decoding sequences of signals, in general, and to the high speed generation and decoding of M-sequence signals, in particular, while using relatively slow circuit components.
2. Prior Art
There are many instances where particular sequences of signals, referred to as M-sequence signals, are required. In typical applications, the M-sequence signals are used in spread spectrum techniques to provide randomization of the data which is to be transmitted. This type of operation reduces the risk of interception and understanding of the transmitted data by unauthorized receivers. Also, the code sequence may be utilized to prevent loss of intelligible information due to jamming. Moreover, an M-sequence circuit guarantees a large number of signal transitions, e.g. binary 1's to binary 0's and vice versa.
These techniques have been used for some time and circuits for generating the sequences, encoding the sequences and/or decoding the sequences are known in the art. However, one of the problems with M-sequence signal generation for spread spectrum communication is that the sequence must be generated at very high signal rates. This tends to be difficult and costly with today's technology. That is, the circuit components which are presently available are relatively slow in operation, even though the circuits can operate in the near megahertz (MHz) range. However, in many instances it is necessary and/or desirable to operate the M-sequence generating circuitry of the type described herein in the gigahertz (GHz) range. Unfortunately, the technology currently available is unable to perform this high speed operation economically.
While it is possible and, perhaps, likely that future technology will become available to operate in this speed range, alternative approaches must be designed at this time to permit the gigahertz range of operation with the megahertz range equipment. The invention described hereinafter accomplishes this operational capability.